CAPOS: The bulge Cluster APOGEE Survey VI. Characterizing multiple stellar populations and chemical abundances in the bulge globular cluster NGC 6569

Abstract

Context. The CAPOS project aims to obtain accurate mean abundances and radial velocities for many elements, and it explores the multiple population (MP) phenomenon in Galactic bulge globular clusters (BGCs). NGC 6569 is one of the CAPOS targets. Aims. This study provides a detailed high-resolution spectroscopic analysis of NGC 6569 to derive precise abundances for elements of different nucleosynthetic origins and to unveil its MPs by focusing on key spectral features. Methods. We analyzed APOGEE-2 near-infrared spectra of 11 giant members with the BACCHUS code, deriving abundances for 12 elements (C, N, O, Mg, Si, Ca, Ti, Fe, Ni, Al, Ce, Nd). Isochrone fitting with Gaia+2MASS photometry was used to estimate atmospheric parameters, cluster distance, and extinction. Results. We obtained [Fe/H] = -0.91 $\pm$ 0.06, consistent with APOGEE pipeline values; the scatter lies within uncertainties. The cluster shows [$\alpha$/Fe] = 0.36 $\pm$ 0.06 dex, similar to other GCs. Al appears homogeneous, while N is strongly enriched ([N/Fe] = 0.68 $\pm$ 0.34) with a spread of 0.90 dex, yielding two populations anticorrelated in C. The n-capture elements Ce and Nd are overabundant compared to the Sun but consistent with GCs of similar metallicity, with $⟨$[Ce/Nd]$⟩$ = -0.17 $\pm$ 0.12. We also measure RV = -49.75 $\pm$ 3.68 km s${}^{-1}$, consistent with previous works, while d${}_{\odot }$ = 12.4 $\pm$ 1.45 kpc and E(B-V) = 0.68 are both higher than literature values. Conclusions. MPs in NGC 6569 are confirmed through a clear C-N anticorrelation. The cluster shows [$\alpha$/Fe] enhancement from Type II SNe and no Mg-Al-Si anticorrelation, suggesting rapid and homogeneous formation. The $⟨$[Ce/Nd]$⟩$ ratio points to contributions from r-process events such as neutron star mergers, while overall Ce and Nd abundances are reported here for the first time in this cluster.

References in corpus (26)

• Array Programming with NumPy
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE) Spectrographs
• Target Selection for the SDSS-IV APOGEE-2 Survey
• The elemental composition of the Sun III. The heavy elements Cu to Th
• Radial variations in the stellar initial mass function of early-type galaxies
• An abundance analysis of bright giants in the globular cluster NGC 1851
• Exploring Anticorrelations and Light Element Variations in Northern Globular Clusters Observed by the APOGEE Survey
• New H-band Stellar Spectral Libraries for the SDSS-III/APOGEE survey
• A large C+N+O abundance spread in giant stars of the globular cluster NGC 1851
• A homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code. I. The Northern clusters
• Atypical Mg-poor Milky Way field stars with globular cluster second-generation like chemical patterns
• NGC 6535: the lowest mass Milky Way globular cluster with a Na-O anti-correlation? Cluster mass and age in the multiple population context
• The Relationship Between Globular Cluster Mass, Metallicity, and Light Element Abundance Variations
• Chemodynamics of newly identified giants with globular cluster like abundance patterns in the bulge, disk, and halo of the Milky Way
• A panchromatic view of the bulge globular cluster NGC 6569
• CAPOS: The bulge Cluster APOgee Survey I. Overview and initial ASPCAP results
• Exploring the Chemical Composition and Double Horizontal Branch of the Bulge Globular Cluster NGC 6569
• CAPOS: the bulge Cluster APOgee Survey II. The Intriguing "Sequoia" Globular Cluster FSR 1758
• Higher order statistics of shear field: a machine learning approach
• Improving spectroscopic lithium abundances. Fitting functions for 3D non-LTE corrections in FGK stars of different metallicity
• APOGEE-2S Discovery of Light- and Heavy-Element Abundance Correlations in the Bulge Globular Cluster NGC 6380
• Formation of globular clusters with internal abundance spreads in r-process elements: strong evidence for prolonged star formation